Field of the Invention
The present invention relates to power supply control in a semiconductor device having an active mode and a standby mode as operation modes.
Description of the Background Art
A semiconductor device such as a microcomputer includes a power supply circuit for generating a power supply voltage (hereinafter also referred to as “internal power supply voltage”) supplied to an internal circuit. Widely used as the aforementioned semiconductor device is a semiconductor device configured to switch the operated power supply circuits based on whether the semiconductor device is in operation (in the active mode) or the semiconductor device is on standby (in the standby mode).
The power supply circuits need to generate the stable power supply voltage both in the active mode and in the standby mode of the semiconductor device. Therefore, the power supply circuit having a high power supply capability is used in the active mode in which power consumption is large and voltage drop occurs easily, whereas the power supply circuit with reduced power consumption is used to achieve lower power consumption in the standby mode in which power consumption is small.
When switch control is executed between an output of an on-chip regulator and an external power supply in a chip having multiple power supplies, it is necessary to sequentially raise a plurality of power supply voltages in accordance with a predetermined power supply startup sequence when power is turned on, so as not to cause a trouble that each circuit is biased in the forward direction. This startup sequence control imposes restrictions on the user. The other problems and novel features will become more apparent from the description of the specification and the accompanying drawings.